Area Forecast Discussion
Issued by NWS Wakefield, VA

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390 FXUS61 KAKQ 090854 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 354 AM EST Fri Dec 9 2016 .SYNOPSIS...
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Canadian high pressure builds into the Mid-Atlantic today, settling over the region tonight into Saturday. The high slides offshore Sunday. Low pressure will push north of the area on Monday, with the associated cold front crossing the region late Monday. Another strong cold front impacts the region during the middle of next week.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Latest surface analysis centers 1045+mb high pressure over Alberta, with a ridge extending southeast into the central and eastern portions of the US. The associated air mass has spilled over the mountains, with dewpoints already dropping into the teens across the forecast area. Temperatures are steadily falling as well, with morning lows still forecast in the mid to upper 20`s. An extension of the Arctic high will break off over the Midwest this morning, and builds eastward into the Ohio Valley late today. Ongoing cold air advection ahead of the building high will result in a cold/brisk day today. 850Mb temperatures drop to around -10C (-2 standard deviations) by this afternoon. Low level thicknesses yield temperatures in the upper 30`s to around 40, so continue to undercut statistical guidance. Highs forecast in the upper 30`s to around 40 (-1 standard deviation) under a sunny sky. A brisk northwest wind of 10-15 mph inland and 15 to 20 mph near the coast is expected and will keep wind chill values in the low to mid 30s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
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Cold, Canadian high pressure builds into the region tonight as the mid level trough axis pushes offshore. Winds decouple away from the coast, with temperatures dropping into the upper teens to around 20 inland to the mid 20`s near the coast. The high finally builds over the mountains, centering over eastern North Carolina Saturday. 850Mb temperatures and low level thicknesses moderate somewhat Saturday thanks to westerly flow, but limited mixing and 850mb temperatures still around -8 to -10C will still result in a cold day. Highs similar to Friday, generally in the upper 30`s to low 40`s under a sunny sky. High pressure remains over the region Saturday night. Meanwhile, a northern stream trough dives into the Great Lakes region, resulting in increasing high clouds late. There should still be several hours of rather ideal radiational cooling conditions with lows again dropping into the low to mid 20`s. The initial wave pushes north of the region Sunday with a secondary wave diving into the Ohio Valley. The surface high slides offshore. Increasing clouds and limited mixing will again result in below normal temperatures. Highs generally in the mid 40`s to low 50`s southeast.
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&& .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
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Sfc high pressure slides offshore by Sun aftn and winds become more sly on Sun. The combination of a weak coastal trough developing off the Carolina Coast Sun night and a warm front lifting north through the area should bring rain up along the Mid Atlantic coastal areas Sun night. A cold front associated with low pressure tracking along the St Lawrence River Valley is then expected to cross the region Mon and exit the coast late Mon night. Winds generally sw ahead of the front...becoming nly Tue. The cooler air behind the cold front is much more modified and what would be typical breezy conditions along the coast are not anticipated at this time. Sfc high pressure returns Tue/Tue night...followed by what could be a developing coastal low off the Southeast into Mid Atlantic coasts on Wed. A brief warm-up should be anticipated as the aforementioned warm front lifts through the region Sun night into early Mon. Areas north of the warm front should remain wedged and keep cooler air in place prior to the initial onset of precip. This could result in a rain/snow mix quickly transitioning to all rain overnight. Precip should remain as rain through Monday. Temperatures generally at to slightly below normal throughout the period.
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&& .AVIATION /09Z FRIDAY THROUGH TUESDAY/... Latest surface analysis depicts cold Canadian high pressure spilling over the mountains early this morning. Scattered to broken high clouds at or above 25k feet AGL persist across the region thanks to fast southwest flow aloft. Expect the high clouds to slide offshore through early morning with clear skies all TAF sites come daybreak. Expect northwest surface winds around 10 knots, with gusts near 20 knots along the coast through early morning. High pressure continues to build into the region today with widespread VFR conditions. Northwest winds of 10-15 knots with gusts around 20 knots expected this afternoon. OUTLOOK...High pressure builds into the area through Saturday. High pressure slides offshore Sunday. There will be a chance for rain Monday as a cold front approaches from the west. Following the passage of the cold front Monday night...dry weather returns for Tuesday. && .MARINE... Have started all SCA flags for the waters with the aftn forecast issuance since winds are expected to increase in the next 3-6 hrs. A strong cold front will cross the waters this evening...followed by a rapidly tightening pressure gradient, strong cold air advection, and a strong 140-160kt jet streak impacting the waters in the post-frontal environment. Overall wind forecast over the waters is on track with w-nw winds increasing to 15-25kt this evening with gusts around 30kt over the ocean/Ches Bay overnight. Speeds stabilize Fri morning (still sustained 15-20kt), and a brief lull in winds to 10-15kt can be anticipated on the rivers during this time. This will be short-lived as a secondary surge in colder air/wind speeds is expected to occur Fri evening...with speeds/gusts increasing by roughly 5kt. Seas build to 4-6ft this evening and overnight... hovering around 4-5ft through early Sat morning. Waves will average 3-4ft during SCA and may also drop to a solid 3ft during the brief lull in winds Fri morning. The cold air finally begins to equalize and the pressure gradient slowly relaxes after midnight Fri night into early Sat as sfc high pressure builds across the OH/TN Valleys and inches closer to the Mid Atlantic Region. The high slides overhead Sat night into Sun morning with light and variable winds. The high then slides offshore by Sun aftn and winds become more sly aob 15kt on Sun. The combination of a weak coastal trough developing off the Carolina coast Sun night and a warm front lifting north through the area should bring rain up along the Mid Atlantic coast Sun night into Mon morning with a brief period of drying during the day on Mon. A cold front associated with low pressure tracking along the St Lawrence River Valley is then expected to cross the waters Mon night and exit the coast by Tue morning. Winds generally sw aob 15kt ahead of the front...becoming nly Tue. The cooler air behind the cold front is much more modified and SCA conditions are not anticipated at this time. Seas average 2-3ft Sat night through Mon and may build up to 5ft briefly on Tue. Waves 1-2ft. && .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ635- 636-638. Small Craft Advisory until 7 AM EST Saturday for ANZ630>632- 634. Small Craft Advisory until 4 AM EST Saturday for ANZ633-650- 652-654-656-658.
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&& $$ SYNOPSIS...AJZ/SAM NEAR TERM...AJZ/SAM SHORT TERM...AJZ/SAM LONG TERM...BMD AVIATION...SAM/LSA MARINE...BMD

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